1. Field of the Invention
The invention relates to processes for recovering or removing solutes from dilute solutions using adsorbent beds.
2. Prior Art
Processes that use adsorbent beds of, for example, ion exchange resin beads to recover metals from natural mine drainage, leachate from piles of ore or process streams from acid leach tanks are known. The adsorbent resin bed after loading with metal values is eluted to produce a concentrated solution suitable for further processing to yield, for example, the pure metal. The resulting solution may, for example, be fed to a conventional electrowinning cell.
A number of processes have been developed for copper recovery that employ moving beds of chelation resins. That is, a portion of the resin bed is removed from a continuously loading resin column for elution of the desired metal. These beds achieve high metal recovery but are characterized by high attrition of expensive chelation resin through breakage of the resin beads during transport to and from the elution column.
A recent moving bed process, described by Himsley in U.S. Pat. No. 4,018,677 avoids valving and other restrictions that destroy the chelation resin beads but achieves only moderate copper recovery. In addition, the Himsley moving bed requires a large resin inventory which requirement adversely effects process economics.
Thus, present adsorptive processes for recovering metals from dilute process or mining streams lack a simultaneous solution to the problems of adequate metal recovery, a reasonable resin inventory and a satisfactory useful life of the resin in the process.